Process recycle streams: identify the wrong statement about how recycling affects reactor feed, conversion, and common unit operations (e.g., reflux in distillation).

Introduction / Context:
Recycle is a foundational concept in chemical process design. By returning unreacted materials to the reactor, a plant can approach higher overall conversion than is possible in a single pass. Recycle is also used widely outside reactors, for example in distillation, where part of the distillate is returned as reflux to improve separation. This question asks you to spot the single incorrect statement about recycle behavior and definitions.

Given Data / Assumptions:

• Single-pass conversion is typically less than 100% for many reactions.
• Recycle returns unreacted reactant(s) back to the reactor feed.
• Combined feed = fresh feed + recycle stream.
• Reflux is a classic internal liquid recycle in distillation columns.

Concept / Approach:
Overall conversion with recycle is higher than single-pass conversion because unreacted reactants get additional opportunities to react. The combined feed ratio is standard: (amount of a reactant in reactor feed) / (amount of that reactant in fresh feed). Reflux is indeed a recycle to maintain internal liquid traffic and improve separation efficiency. Therefore, any claim that recycle does not help increase overall extent of reaction is wrong.

Step-by-Step Solution:

Verification / Alternative check:
Material balance around a reactor with recycle shows the same per-pass kinetics, but overall unreacted loss decreases as recycle increases (until limited by equilibrium, kinetics, or economics).

Why Other Options Are Wrong:

• (a) Correct: recycle reduces purge losses of unreacted reactants.
• (b) Correct: textbook definition of combined feed ratio.
• (d) Correct: reflux is a recycle stream in distillation.
• (e) Correct: recycle can damp hot spots and tune residence time.

Common Pitfalls:
Confusing single-pass conversion (which may be unchanged) with overall plant conversion (which increases with recycle and/or purge management).

Final Answer:
Recycling does not help in achieving a higher overall extent of reaction.